I want the freedom to ride in the middle of the lane when there are no cars, but if a car gets to 50-100 meters behind me, I want to get over to the side so as not to have them have to slow down or move over. I like riding in the clean part of the road, but don't want to tick off drivers by doing so.

I can hear cars coming up behind me, but by the time I do, they're generally closer than the 50 or so yards. And if cars are going the other direction, I don't hear cars coming up behind me over the sound of the other cars.